1. Field of the Invention
The present invention relates generally to nipple attachments and more specifically it relates to a molded nipple connection system for permanently molding a metal nipple within a plastic container that is not susceptible to expansion/contraction forces incurred by the plastic container.
2. Description of the Prior Art
Nipple attachments have been in use for years. Typically, the nipple is molded from plastic directly within the container. Since a sealing cincture or threads are usually required within the nipple for attaching to a hose or coupler, the mold's halves meet at the plastic nipple portion to allow the molds to be removed from the nipple portion. This causes an undesirable longitudinal plastic "ridge" to be formed into the nipple because of leakage of plastic between the mold's halves. This ridge prevents a proper seal or threading onto the nipple. Therefore, conventionally the ridge must be removed by grinding or other process. During the removal process, it is almost impossible to perfectly remove the ridge, either removing to much plastic or not enough. Hence, a perfect seal is never achieved using conventional molding methods.
Molding a metal nipple within a mold has also been attempted with limited success. A metal nipple is more desirable than a plastic nipple of its ability to resist wearing over time. The most common problem is that the metal nipple will become dislodged overtime allowing the nipple to rotate and/or become removed. Additionally, extreme temperatures cause the plastic to contract and expand thereby loosening the plastic from the nipple. Also, forces applied to the plastic container can cause the container to expand around the nipple allowing the nipple to be removed from the container.
Examples of nipple attachments include U.S. Pat. No. 4,679,405 to Mitchell et al; U.S. Pat. No. 3,614,137 to Jacobson; U.S. Pat. No. 5,366,257 to McPherson et al; U.S. Pat. No. 4,292,846 to Barnett; U.S. Pat. No. 4,572,386 to Marcus; U.S. Pat. No. 4,960,342 to Chi which are all illustrative of such prior art.
Mitchell et al (U.S. Pat. No. 4,679,405) discloses a molded drain connection with insert. Mitchell teaches an integrally threaded brass insert molded into a discharge conduit of a condensate pan such that a steel drainage pipe can be threadably engaged to the insert without causing damage to the plastic discharge conduit. Mitchell further teaches the use of a "knurled" surface on the outer periphery of the insert to prevent removal. This structure is still susceptible to the expansion of the plastic due to forces and temperature thereby allowing the insert to be dislodged.
While these devices may be suitable for the particular purpose to which they address, they are not as suitable for permanently molding a metal nipple within a plastic container that is not susceptible to expansion/contraction forces incurred by the plastic container. The prior art inventions are easily removed from the plastic container they are molded within. Additionally, the molded plastic nipples are not desirable because of inherent sealing problems.
In these respects, the molded nipple connection system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing provides an apparatus primarily developed for the purpose of permanently molding a metal nipple within a plastic container that is not susceptible to expansion/contraction forces incurred by the plastic container.